Determining tobacco weight

ABSTRACT

Apparatus is disclosed for determining the weight of tobacco in a tobacco product ( 10 ), the tobacco product comprising a tobacco component ( 16 ) and a plurality of non-tobacco components ( 12, 14, 18, 20, 22 ). The apparatus comprises means ( 26 ) for determining the total weight of the tobacco product ( 10 ), means ( 30 ) for producing an x-ray image of the tobacco product, means ( 34 ) for determining weights of the non-tobacco components from the x-ray image, and means ( 34 ) for determining the weight of the tobacco component based on the total weight of the tobacco product and the weights of the non-tobacco components. This may allow an accurate determination of tobacco weight to be achieved. Furthermore, measurements can be taken where components are present which might interfere with microwave measurements.

The present invention relates to techniques for determining tobacco weight, and in particular the weight of tobacco in tobacco products such as heated tobacco products.

New types of tobacco products known as heated (or heat not burn) tobacco products have been developed mainly as a response to the health risks associated with smoking tobacco. These products are characterised by heating the tobacco without combustion or smouldering to release an aerosol containing nicotine and flavours which the user inhales. Heated tobacco products come in various forms, including products which are heated by a separate electronic device, and products in which the tobacco is heated by a carbon tip that is separated from the tobacco.

Heated tobacco products have varying constructions depending on the manufacturer but typically will be in the form of a rod with a tobacco element, a filter element, and a transfer tube. Other physical components may be present such as carbon blocks, flavour capsules, foils, metal strips and so on. The rod may be wrapped with paper to hold it together in a form not unlike a conventional cigarette, and may further include tipping paper and flavours such as menthol.

During manufacture of any tobacco product, the control of tobacco weight is considered a key manufacturing parameter. Excess tobacco in the product will adversely impact profits and could result in increased yields of toxicants. On the other hand, too little tobacco could result in consumer dissatisfaction. It is therefore known to perform measurements of tobacco density and/or weight as part of the making process.

Conventionally, the measurement of tobacco density and weight is made using microwave resonator cavities. These techniques work by measuring a change in microwave resonance caused by a tobacco rod passing through the cavity. This effectively provides a measure of the density of the rod which can be simply converted to the tobacco weight of the rod. The microwave technique may also be deployed for tobacco weight measurement offline as part of quality control and quality assurance activities.

Some finished tobacco products contain metal components such as bands, foils and wrappers which may interfere with the working of the microwave cavity and render the density measurements unreliable. Furthermore, other elements such as a carbon block adjacent to a tobacco column could produce a strong microwave response. Therefore, the microwave measurement of tobacco weight or density may not be suitable where there is an interference caused by a non-tobacco component in the tobacco product.

X-ray weight measurement systems have been trialled as replacements for the microwave weight systems. For example, WO 2019/073214, the subject matter of which is incorporated herein by reference, discloses a method of using x-rays to determine the density of a tobacco product as it travels in a longitudinal direction through an inspection zone. Such techniques use the density of the image produced by an x-ray source and detector to infer the weight of tobacco using a nominal density of tobacco against image density calibration.

A problem in known x-ray weight measurement systems is that the density of the image is subject to a number of variations that are not related to a change in the amount of tobacco present. For example, the image brightness, density and saturation are a function of the source brightness and this is known to vary with time. Furthermore, the detector sensitivity may change with time. This means that the image usually gets darker with time which would imply that there was more tobacco in the rod. The consequence is that a calibration of image density to true physical density cannot hold with time and any change in parts or conditions could need a new calibration which would be complex and tedious.

In addition, changing the blend or type of tobacco would necessitate a new calibration as it is unlikely that one type of tobacco (for example, laminar) would have the same image density and physical density characteristics as other types (for example DIET expanded tobacco).

Furthermore, as the tobacco component is typically nonhomogeneous, the way the tobacco is packed into the tobacco product can have a confounding effect on the direct determination of density. For example, the orientation of strands and their relationship to other strands in the cigarette may change the image density. It has been found that, for example, rotating the same product through 90° could give two average image densities that varied significantly and would be translated to a 10-20% error in tobacco weight.

It would therefore be desirable to provide techniques which can allow more accurate determination of weight of tobacco in a tobacco product, which can be used in cases where other components might cause interference with microwave measurements, and/or which are less sensitive to drift in accuracy.

According to one aspect of the present invention there is provided apparatus for determining the weight of tobacco in a tobacco product, the tobacco product comprising a tobacco component and a plurality of non-tobacco components, the apparatus comprising:

-   -   means for determining the total weight of the tobacco product;     -   means for producing an x-ray image of the tobacco product;     -   means for determining weights of the non-tobacco components from         the x-ray image; and     -   means for determining the weight of the tobacco component based         on the total weight of the tobacco product and the weights of         the non-tobacco components.

The present invention may provide the advantage that, by determining the weights of the non-tobacco components from an x-ray image, and determining the weight of the tobacco component based on the total weight of the tobacco product and the weights of the non-tobacco components, a more accurate determination of tobacco weight may be achieved than with conventional techniques. Furthermore, the present invention may allow measurements to be taken where components are present which might interfere with microwave measurements. In addition, the present invention may be less susceptible to drift in accuracy than conventional techniques.

The present invention may be used with any type of tobacco product containing a tobacco component and non-tobacco components, such as conventional cigarettes. However, the present invention is particularly applicable to more complex tobacco products, such as heated tobacco products, which may be more difficult to analyse using conventional techniques. Thus, the tobacco product may be a heated tobacco product.

The tobacco product may be a rod-shaped article. In this case at least some of the components of the tobacco product may be substantially cylindrical. For example, the tobacco product may comprise one or more of a filter, a tube, a tobacco column and a carbon block each of which may be substantially cylindrical. The tobacco product may also comprise one or more components in sheet form, such as a metal foil and a paper overwrap. Such components may be wrapped around the rod-shaped article.

The tobacco component may comprise reconstituted sheet tobacco. Such tobacco components are typically found in heated tobacco products and may be difficult to analyse using conventional techniques.

The tobacco product may comprise a component which produces a microwave response independent of product density when irradiated with microwaves. For example, the tobacco product may include a metal component such as a metal foil, band or overwrap, and/or a carbon component such as a carbon block or a filter element infused with carbon granules. In one example, the tobacco component is at least partially over-wrapped with a metal or metalized foil. The present invention may avoid the use of microwaves and thus may facilitate the analysis of such products.

Preferably the means for determining the weight of the tobacco component is arranged to subtract the weight of each of the non-tobacco components from the total weight of the tobacco product.

In one embodiment, the means for determining weights of the non-tobacco components is arranged to determine the weight of at least one of the non-tobacco components directly. This may be done, for example, based on the optical density of the component in the x-ray image.

However, in a preferred embodiment, the means for determining the weights of the non-tobacco components is arranged to determine a dimension of each of the non-tobacco components, and to calculate the weight of the component based on the dimension. The dimension may be, for example, at least one of a length and a diameter of the component. The dimension of a component may be mapped directly or indirectly to its weight. It has been found that such indirect determination of the weights of the non-tobacco components may produce more accurate results and may be less susceptible to drift.

The means for determining the weights of the non-tobacco components may comprise means for analysing the x-ray image to determine a dimension of each of the non-tobacco components. This may provide a convenient and reliable way of determining the dimensions of the components of a tobacco product.

The means for determining the weights of the non-tobacco components may be arranged to calculate a volume or an area of each of the non-tobacco products based on the dimension (for example, the dimension as determined by the image analysis means). For example, where the component is a solid component, the volume of the component may be calculated. Where the component is in sheet form, either the volume or the area of the component may be calculated. The calculation of the volume or area may be achieved, for example, using a formula based on knowledge of the shape of the component. The shape of the component may be predetermined or may be inferred from the x-ray image.

For example, where the component is a solid cylinder, the volume of the component may be calculated from the equation V=π(D/2)²L, where V is volume, D is diameter and L is length. Where the component is a hollow cylinder the volume of the component may be calculated from the equation V=π((ED/2)²— (ID/2)²) L, where ED is external diameter and ID is internal diameter. Where the component is in the form of a sheet of material, such as a paper overwrap, the area of the component may be calculated from A=πDL.

It has been found that, for some products, the diameter may vary little from one product to another. Thus, in one embodiment, the diameter of a component may be a predetermined value, and the length of the component may be determined from the x-ray image. However, if desired, any appropriate dimension may be determined from the x-ray image and used in the weight determination.

Preferably, the means for determining the weights of the non-tobacco components is arranged to determine the weight of a non-tobacco component based on a volume or area of the component and a predetermined value of density or area density for that component. For example, the volume of a component may be multiplied by a predetermined value of density to obtain the weight. In another example, the area of a component may be multiplied by a predetermined value of area density to obtain the weight. Alternatively, the length (or any other dimension) of a component may be mapped directly to weight. It has been found that, for a typical product, the densities of the non-tobacco components tend not to vary significantly from one product to the next. Thus, these techniques may provide a relatively accurate way of determining the weights of the non-tobacco components.

The apparatus may be for use with a plurality of different types of products, each of which may have components with different characteristics. In this case, the apparatus may further comprise storage means (memory) which stores predetermined values of density or area density of non-tobacco components for each of a plurality of different types of tobacco product. The means for determining the weights of the non-tobacco components may be arranged to look up the predetermined values of density or area density in the storage means for a product of the type which is under test. This can allow the apparatus to be easily adapted to different types of product, or where the composition of a product is changed.

In one embodiment, the means for determining the weights of the non-tobacco components is arranged to determine the type of product which is under test based on characteristics of the tobacco product in the x-ray image. Alternatively, the type of product may be input by the user.

The means for producing an x-ray image may comprise:

-   -   a source of x-ray radiation arranged to irradiate the tobacco         product; and     -   a sensor arranged to detect x-ray radiation from the tobacco         product and to produce the x-ray image.

In one embodiment, the sensor is a flat panel x-ray detector or a line scanner. The means for producing an x-ray image may be arranged to produce a composite x-ray image from image data produced by the sensor at a plurality of different axial positions of the tobacco product. This may provide a convenient and cost-effective way of producing the x-ray image.

The means for producing an x-ray image may further comprise means for holding the tobacco product while it is being imaged. The means for holding the tobacco product may be arranged to apply a vacuum to the tobacco product and/or to hold the tobacco product physically. The means for holding the tobacco product may be, for example, a vacuum chuck, or any other suitable device for holding the tobacco product.

Preferably the means for producing an x-ray image is arranged to produce an image of the whole of the tobacco product. This may be achieved, for example, by taking an image of the whole of the product, or by taking images of different parts of the product and combining the images to obtain an image of the whole of the product.

The means for determining the total weight of the tobacco product may be a weighing device such as a weight balance, or any other appropriate device for determining weight of an article.

In one embodiment, the apparatus is an analysing apparatus for offline analysis of tobacco products.

In another embodiment, the apparatus is part of a tobacco product making or combining machine. In this case, the means for determining the total weight of the tobacco product may be part of the machine.

Where the apparatus is part of a tobacco product making or combining machine, the weight of the tobacco component (as determined by the apparatus) may be used to control filling of the tobacco component of tobacco products produced by the machine. This can allow automatic control of the quantity of tobacco. Alternatively, the weight of the tobacco component may be displayed and used by an operator to control the machine.

According to another aspect of the invention there is provided a tobacco product making or combining machine comprising an apparatus in any of the forms described above.

In any of the above arrangements, the means for determining the weights of the non-tobacco components and/or the means for determining the weight of the tobacco component may be implemented as one or more software modules running on a suitable processor with associated memory. Thus, the apparatus may comprise processing means, such as a processor programmed with computer software, arranged to carry out any of the functions described above.

In any of the above arrangements, means may be provided for conveying the tobacco product to, within and/or from the apparatus. For example, the apparatus may comprise a product feed mechanism for feeding the tobacco product to the apparatus and/or a product transfer mechanism for transferring the tobacco product from one part of the apparatus to another, and/or an ejection mechanism for ejecting the tobacco product from the apparatus. The means for conveying the tobacco product apparatus may operate under control of a control unit, which may be implemented as a software module on a processor.

Corresponding method aspects may also be provided. Thus, according to another aspect of the invention there is provided a method of determining the weight of tobacco in a tobacco product, the tobacco product comprising a tobacco component and a plurality of non-tobacco components, the method comprising:

-   -   determining the total weight of the tobacco product;     -   producing an x-ray image of the tobacco product;     -   determining the weights of the non-tobacco components from the         x-ray image; and     -   determining the weight of the tobacco component based on the         weight of the tobacco product and the weights of the non-tobacco         components.

Features of one aspect of the invention may be provided with any other aspect. Apparatus features may be provided with method aspects and vice versa.

Preferred features of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which:

FIG. 1 shows parts of a typical heated tobacco product;

FIG. 2 shows parts of an apparatus for determining the weight of tobacco in a tobacco product in an embodiment of the invention;

FIG. 3 shows parts of an x-ray system;

FIG. 4 shows parts of a tobacco weight determination unit in one embodiment;

FIGS. 5A and 5B show examples of an x-ray image of a tobacco product; and

FIG. 6 shows parts of a system for manufacturing and analysing tobacco products.

The ways in which smoking articles are constructed has been changed fundamentally by the advent of a new class of heated tobacco product. These products, sometimes referred to as heat-not-burn products or heat-not-burn sticks, are characterised by the heating of tobacco, rather than combustion, in order to produce fewer hazardous substances.

For example, one type of heated tobacco product, sometimes referred to as a “heat stick”, consists of a reconstituted tobacco plug, filter and cooling elements wrapped in paper. The reconstituted tobacco is high in glycerine/propylene glycol. In use, the sticks are inserted into a pen-like holder which includes a heater. The tobacco is heated to a temperature of up to 350° in the holder. The nicotine containing aerosol released is inhaled by the consumer. The construction of the heat stick may be, for example, as disclosed in EP 2854569, the subject matter of which is incorporated herein by reference. Although the format of this type of product is relatively simple, more complex constructions are available.

Some other types of heated tobacco product rely on the use of a metal foil surrounding elements of the heated tobacco stick to transfer heat from the heat source to the tobacco or tobacco sheet. For example, one type of product contains an internal heat source in the form of a piece of coal provided with air channels and containing an oxidation means. The coal is used to heat a plug of two reconstituted tobaccos which have aerosol-generating properties. When drawing on the product, the glowing piece of coal heats the sucked-in air to approximately 300° C. and vaporizes the heated air aerosol from the tobacco. An example of this type of heated tobacco product is disclosed in US 2007/0023056, the subject matter of which is incorporated herein by reference. Other types of tobacco product may also have a metal foil surrounding some or all of the tobacco column.

During manufacture of any tobacco product the control of tobacco weight is considered a critical one. The tobacco is normally the most expensive part of the product, and therefore excess tobacco will adversely impact profits whilst too little tobacco could result in consumer dissatisfaction. Additionally, excess tobacco in the product could result in increased yields of toxicants that need to be reported to regulating authorities. In extreme cases this could result in product quarantine/reject as part of batch release or even product market withdrawal. Hence control of weight of tobacco, in effect through monitoring and control of density, is a key manufacturing parameter.

The measurement of density or weight of tobacco may be performed online as part of the making process. Conventionally this is performed through the use of microwave resonator cavities, such as that disclosed in U.S. Pat. No. 7,132,836. These methods work by measuring a change in microwave resonance caused by a tobacco rod passing through the cavity. This effectively provides a measure of the density of the rod which can be simply converted to the tobacco weight of the rod. The microwave method may also be deployed for tobacco weight measurement offline as part of quality control and quality assurance activities.

It has been found that, where the tobacco product contains an element which produces a high microwave response adjacent to a segment of interest, the high response of the microwave will tend to obscure the true response of the segment of interest. As an example, a carbon block adjacent to a tobacco column could produce a strong microwave response. In this case, the tail of the response for the carbon may interfere with the microwave measurements by changing the apparent length of the element under test or causing a misestimation of the tobacco density.

It is also known that some finished tobacco products contain metal components such as gold bands and wrappers which may interfere with the working of the microwave cavity and render the density measurements unreliable. Thus, the microwave measurement of tobacco weight or density may not be suitable where there is an interference caused for example by a metal foil overlap or overwrap in a tobacco rod or in the completed heated tobacco product.

Thus, it has been found that the microwave method is not effective with certain types of tobacco product. However, without some means of control it is possible that the incorrect amount of tobacco will be added to the product, usually over filling to err on the side of safely which has the result of higher than necessary product cost and subsequent loss of profit.

X-ray systems have been trialled to replace the microwave weight systems. These systems rely on discriminating the x-ray optical density of the tobacco column. However, as the tobacco column is essentially nonhomogeneous, such systems have not proved effective. In tests, significantly variable results were obtained on the same sample just through the act of product rotation. An accuracy of ±15% was a practical limit for such a system where only x-ray image density of the tobacco column was utilised.

Thus, it has been found that measurement of density of the tobacco column based on optical systems or direct x-ray density measurement cannot reliably be used to form a measurement of the weight of tobacco.

Embodiments of the invention use a combination of total weight measurement of the finished product and measurements of the dimensions of components of the product that have uniform densities. The weight of the tobacco component which may not have a uniform density can then be determined. This can allow the non-destructive determination of the weight of tobacco in a heated tobacco product which may include metal components such as a metal foil overlap of the tobacco column.

FIG. 1 shows parts of a typical heated tobacco product. Referring to FIG. 1 , the tobacco product 10 comprises a filter plug 12, a tube section 14, a tobacco column 16, a carbon tip 18 with air perforation holes, an aluminium foil 20, and an overwrap of paper 22. The filter plug 12 is made of a material of uniform density such as cured cellulose monoacetate. The tube section 14 is used to cool the aerosol, and may be made of carboard or more usually steam cured hollow acetate tube. The tobacco column 16 is made of reconstituted tobacco of non-uniform density. The aluminium foil 20 covers part of both the carbon tip 18 and the tobacco column 16. In use, the carbon tip 18 is lit and acts as a heat source to heat the tobacco column 16 via the aluminium foil 20.

It will be appreciated that the exact construction of a heated tobacco product may vary depending on the manufacturer and the product line, so this description is given by way of example rather than limitation. For example, in other constructions, one or more of the components may be absent, one or more additional components may be present, and/or the size and/or relationship of the components may vary.

It has been found that, in a product such as that shown in FIG. 1 , all components except for the tobacco column tend to have consistent, uniform densities for a specific type of product. These densities can be measured in bulk and recorded. This can allow the weight of those components to be determined with a reasonable degree of accuracy. If the product is placed in an apparatus that combines the ability to weigh the whole product and determine the exact physical dimensions of the non-tobacco components of the tobacco product, it is possible to infer the weight of the tobacco component.

FIG. 2 shows parts of an apparatus for determining the weight of tobacco in a tobacco product in an embodiment of the present invention. Referring to FIG. 2 , the apparatus comprises product feed 24, balance 26, product transfer 28, x-ray system 30, product ejector 32, tobacco weight determination unit 34, display unit 36, and control unit 38. In operation, the product feed 24 receives a tobacco product 10, for example, from a hopper or a mass flow, and passes the tobacco product to the balance 26. The balance 26 measures the total weight (mass) of the tobacco product, and sends data indicating the total weight to the tobacco weight determination unit 34. Once the weight of the tobacco product has been measured, the product transfer 28 transfers the tobacco product 10 from the balance 26 to the x-ray system 30. The x-ray system 30 produces one or more x-ray images of the tobacco product and passes the images to the tobacco weight determination unit 34. The product ejector 32 then ejects the tobacco product 10, for example to a collection bin or to other equipment for further analysis. The tobacco weight determination unit 34 receives the total weight of the tobacco product from the balance 26 and the images from the x-ray system 30, and from these determines the weight (mass) of the tobacco, as will be explained below.

The various parts of the apparatus are operated under control of the control unit 38. The control unit 38 communicates with the various parts of the apparatus using a system bus 40 which operates using a suitable communications protocol. For simplicity, connections between the control unit 38 and the other parts of the apparatus are not shown in FIG. 2 .

In the arrangement described above, the product feed 24, product transfer 28 and product ejector 32 include transfer mechanisms in order to transfer the tobacco product from one part of the apparatus to another. Such transfer mechanisms are known in the art and therefore not described further.

The balance 26 is an analytical balance that measures the total mass of the tobacco product to a high degree of precision. Data relating to the total mass of the tobacco product is transferred to the tobacco weight determination unit 34 using a suitable communications protocol. Such balances are commercially available, and therefore not described further.

The x-ray system 30 includes an x-ray source and an x-ray detector. In one embodiment, the x-ray system 30 employs a fast-acting solid-state panel x-ray detector or a scanning system in order to produce x-ray images of the tobacco product. Alternatively, the x-ray system may comprise a detector which is arranged to take x-ray images of the entire tobacco product.

The tobacco weight determination unit 34 contains algorithms for analysing the x-ray images of the tobacco product and determining the weight (mass) of the tobacco, as will be explained below. The tobacco weight determination unit 34 may be implemented as one or more software routines executing on a suitable processor, such as personal computer.

It will be appreciated that, in alternative arrangements, the x-ray system 30 could be before the balance 26, or the x-ray system 30 and the balance 26 could be part of the same system (for example, the x-ray images could be taken at the same time as the product is being weighed).

FIG. 3 shows parts of the x-ray system 30 in one embodiment. Referring to FIG. 3 , the x-ray system comprises an x-ray source 42, x-ray panel detector 44, vacuum chuck 46, platform 48, drive motor 50, leadscrew 51, positional encoder 52 and control and processing unit 54. The vacuum chuck 46 is used to hold a sample 10 using a vacuum. The vacuum chuck 46 is attached to the platform 48, which is translated by means of the motor 50 and leadscrew 51. The leadscrew 51 is aligned with the axis of the sample 10, such that rotation of the motor 50 causes the sample to move axially with respect to the source 42 and the detector 44. The control and processing unit 54 is used to control the operation of the motor 50 in order to move the sample 10 into the appropriate position for imaging. The exact positional reference to the vacuum chuck is measured by the positional encoder 52 and sent to the control unit 54.

In operation, the sample 10 is first moved to a position in which an area of interest is in the field of view of the detector 44. Images of the sample are then taken by the panel detector 44 and transferred to the control and processing unit 54. The sample is then moved axially to another position. In this position additional images are taken and transferred to the control and processing unit 54.

This process may be repeated for a number of different positions of the sample. Preferably, the sample is moved such that images are taken along its entire length, with each image abutting or overlapping with the next. If desired, certain parts of the sample may be imaged as the sample is moving and/or with a reduced exposure time compared to other parts. The control and processing unit 54 includes a suitable imaging algorithm for producing a composite image based on the individual images of different areas of the sample taken by the panel detector 44. The thus produced image data are transferred to the tobacco weight determination unit 34.

If desired, two or more panel detectors could be used in order to image the sample at different circumferential and/or axial positions. Alternatively, a line detector could be used instead of the panel detector.

The x-ray system may be, for example, as described in International patent application number WO 2020/012162, the subject matter of which is incorporated herein by reference, although other types of x-ray imaging systems could be used instead.

FIG. 4 shows parts of a tobacco weight determination unit 34 in one embodiment of the invention. Referring to FIG. 4 , the tobacco weight determination unit 34 comprises image analysis module 56, product type indicator 58, non-tobacco weight calculation module 60, database 62 and tobacco weight calculation module 64.

In operation, the image analysis module 56 receives image data from the x-ray system 30. The image analysis module 56 is arranged to process the image data to determine the dimensions of various components in the tobacco product. In order to achieve this, the image analysis module 56 utilises one or more known algorithms for detecting an edge of an object in a digital image. Such algorithms typically involve measuring contrast levels for defining a point at which an edge is defined as being present, and the length (in pixels) along the defined edge which is used to determine a contiguous and true edge, and involve statistical considerations to determine the probability that a detected edge is a true edge. Edges are detected by analysing horizontal and vertical region projections of the image. Examples of suitable imaging algorithms are disclosed in WO 2004/083834, the subject matter of which is incorporated herein by reference. Such algorithms are known in the art and therefore not described further.

FIGS. 5A and 5B show examples of an x-ray image of a tobacco product produced by the x-ray system 30. Referring to FIG. 5A, various components of the tobacco product can be detected in the x-ray image. In this example, component A is a hollow acetate tube, component B is a first tobacco element containing one blend of tobacco, component C is a second tobacco element containing another blend of tobacco, component D is a carbon tip, component E is an aluminium foil, and component F is a paper overwrap.

FIG. 5B shows various measurements which are performed on the x-ray image by the image processing algorithms in the image analysis module 56 in one embodiment. Referring to FIG. 5B, in this example the image analysis module calculates the length LA of the hollow acetate tube A, the length LB of the first tobacco element B, the length Lc of the second tobacco element C, the length LD of the carbon tip D, the length LE of the aluminium foil E, and the length LF of the paper overwrap F.

The image analysis module 56 may be arranged to determine which one of a plurality of different types of tobacco product the sample belongs to, based on characteristics of the product in the image data. This may be done by using the dimensions measured by the image processing algorithms to look up the product type in the database 62. The product type may then be stored in the product type indicator 58.

For example, in the sample of FIGS. 5 , the lengths of the various components of the product may be different for different types of product. In this case, the database 62 may store a list of tobacco product types with the nominal lengths of one or more of the components for each type. The image analysis module 56 may then use the measured lengths L, to look up in the database 62 the product type to which the sample belongs.

Alternatively, the type of product may be input into the product type indicator 58 by the user via a user interface.

Referring back to FIG. 4 , the dimensions L, of the various components of the tobacco product are output from the image analysis module 56 to the non-tobacco weight calculation module 60. The non-tobacco weight calculation module 60 uses the dimensions L, to calculate the volume (or area) of each of the various components. Typically, for a solid component the volume will be calculated, while for sheet component the area may be calculated. The calculation may be carried out using knowledge of the shape of the component.

The shape of the component may be a standard value or may be retrieved from the database 62 using knowledge of the type of product as indicated by the product type indicator 58.

Typically, components such as the hollow acetate tube A and the carbon tip D shown in FIG. 5 are cut from longer lengths of material. In this case, there may be some variation in the length of the component from one product to another. On the other hand, dimensions such as the diameter of the component may be fairly consistent. Thus, it may be sufficient to measure the length only of some or all of the components. However, if desired, other dimensions in the image could also be measured. For example, the diameter of one or more of the components could be measured. In the case of the hollow acetate tube, the internal and the external diameters could be measured. In this case dimensions such as diameter could be used as well as length in order to estimate the volume or area of the various components of the tobacco product.

The non-tobacco weight calculation module 60 then obtains the density (or area density) of each of the components from the database 62. The database 62 stores, amongst other things, nominal values of density or area density (mass per unit area) for each of the non-tobacco components of each tobacco product type with which the apparatus is used. The non-tobacco weight calculation module 60 uses knowledge of the product type, as indicated by the product type indicator 58, to look up the densities (or area densities) of the components of that product type which are stored in the database 62.

The non-tobacco weight calculation module 60 then uses the volume (or area) of each of the various non-tobacco components of the product (as calculated from the dimensions L,) together with the density (or area density) of that component (as retrieved from the database 62) to calculate the weight of that component.

For example, in the case of the sample shown in FIGS. 5 , the non-tobacco weight calculation module 60 first calculates the volumes of the hollow acetate tube A, the carbon tip D and the aluminium foil E. The volume of the hollow acetate tube A is calculated using the following equation:

V _(A) =X _(A) L _(A)

where XA is the cross-sectional area of the hollow acetate tube A. The cross-sectional area XA may be a predetermined value which is stored in the database 62 for a product of that type (as indicated by the product type indicator 58).

Alternatively, the cross-sectional area XA may be calculated from the internal and external diameters of the hollow acetate tube A, as measured by the image analysis module 56, using the following equation:

$X_{A} = {\pi\left( {\left( \frac{{ED}_{A}}{2} \right)^{2} - \left( \frac{{ID}_{A}}{2} \right)^{2}} \right)}$

Where EDA is the external diameter and IDA is the internal diameter of the hollow acetate tube A.

The volume of the carbon tip D is calculated using the following equation:

V _(D) =X _(D) L _(D)

where X_(D) is the cross-sectional area of the carbon tip D. The cross-sectional area X_(D) may be a predetermined value which is stored in the database 62 for a product of that type, or it may be calculated from the diameter of the carbon tip, as measured by the image analysis unit 56, using the equation:

$X_{D} = {\pi\left( \frac{D_{D}}{2} \right)}^{2}$

where D_(D) is the diameter of the carbon tip D.

The volume of the aluminium foil E is calculated using the following equation:

V _(E) =X _(E) L _(E)

where XE is the cross-sectional area of the aluminium foil E. The cross-sectional area XE may be a predetermined value which is stored in the database 62 for a product of that type, or it may be calculated from dimensions measured by the image analysis unit 56, for example in a similar way to the hollow acetate tube A.

The non-tobacco weight calculation module 60 calculates the area of the paper overwrap F using the following equation:

A _(F) =πD _(F) L _(F)

where DF is the diameter of the paper overwrap. This value may be a predetermined value stored in the database 62 for a product of that type, or it measured by the image analysis unit 56.

The non-tobacco weight calculation module 60 then obtains the densities of the hollow acetate tube A, the carbon tip D and the aluminium foil E and the area density of the paper overwrap F from the database 62. The database 62 includes a look up table which allows the weight calculation module 60 to retrieve the various densities and area density for the non-tobacco components of the tobacco product under test, as indicated by the product type indicator 58.

The weight calculation unit 60 then calculates the weights of the hollow acetate tube A, the carbon tip D and the aluminium foil E using the following equations:

W _(A) —P _(A) V _(A)

W _(D) =P _(D) V _(D)

W _(E) P _(E) V _(E)

where pA, pD and pE are the densities of the hollow acetate tube A, the carbon tip D and the aluminium foil E respectively.

The non-tobacco weight calculation module 60 also calculates the weight WF of the paper overwrap F using the equation:

W _(F) =P _(F) A _(F)

where PF is the area density (mass per unit area) of the paper overwrap.

If desired, the weight of the aluminium foil could be calculated from its area and area density, rather than volume and density, in a similar way to the paper overwrap.

Referring back to FIG. 4 , the weights W, of the various non-tobacco components are output from the non-tobacco weight calculation module 60 to the tobacco weight calculation module 64.

The tobacco weight calculation module 64 calculates the weight of the tobacco in the product based on the total weight of the tobacco product received from the balance 26 and the weights W, of the various non-tobacco components. This is done by subtracting the various weights W, from the total weight. The weight of the tobacco W_(TOB) is then output to the display 36 and/or to other equipment for further processing.

For example, in the case of the sample shown in FIGS. 5 , the tobacco weight calculation module 64 receives the weights WA, WD, WE and W_(F) from the non-tobacco weight calculation module 60 and the total weight WT of the tobacco product from the balance 26. The tobacco weight calculation module 64 then calculates the weight W_(TOB) of the tobacco in the product using the following equation:

W _(TOB) W _(T) −(W _(A) +W _(D) +W _(E) +W _(F))

The weight of the tobacco is then output to the display 36 where it is displayed to the user. The tobacco weight can also be communicated to other pieces of equipment.

Practical tests have shown that the above techniques can have an accuracy of better than 5%, compared with an accuracy of around 15% where the x-ray image density of the tobacco component was utilised directly.

During manufacturing there will be limits placed on an acceptable tobacco weight. The calculated tobacco weight can be plotted in the form of a control chart with action limits against these values allowing the process to be more closely controlled. Alternatively, as part of a making or combining system working at high speed the calculated tobacco weight can be used as a control parameter to vary the filling power of the making or combining device as a part of a closed loop feedback system.

Thus it will be appreciated that embodiments of the invention involve the combined use of a balance plus an x-ray system to determine the weight of a tobacco component of indeterminate density when covered by a foil or other wrapper that precludes the use of microwaves to determine the tobacco weight/density. An x-ray or other optical system is used to provide dimensional information of non-tobacco components within the product. By using the known uniform densities of these stable components, a measurement of their weights can be produced. From these measurements and the total product weight, the weight of the tobacco component(s) with variable or indeterminate density can be derived. This arrangement can be used where the tobacco component is fully or partially over-wrapped with a metal or metalized foil, which would prevent the use of microwaves to determine density. This arrangement can also be used where the tobacco component is closely coupled or adjacent to an element, such as a carbon block or monoacetate filter element infused with carbon granules (such as a “dalmatian” filter), that has a high microwave response that would interfere with the accurate determination of the density using microwaves. These techniques can be used with any type of tobacco product, although they have particular application with heated tobacco products.

The measurements can be made in an offline system comprising a weight balance and an x-ray system, either using a panel or line scan detection. Alternatively, the measurements can be made online as part of a making or combining machine where the total weight measurement is part of the making machine, and where each product is x-rayed to determine the component dimensions and so the component weights. In this case the measurements/derived values of tobacco weight can be used to control the maker or combiner filling of the tobacco portion of a tobacco product.

It has been found that the techniques proposed above where x-rays are used for the location of dimensions is relatively insensitive to changes in source brightness or detector sensitivity and thus drift in accuracy is reduced in comparison to previous techniques. Typically, the only calibration changes that are needed is when different papers or filter tow is used—these are just numbers in the final algorithm and may be obtained from the material specification.

FIG. 6 shows parts of a system for manufacturing and analysing tobacco products. The system comprises a tobacco product making machine 70, a sampling unit 72, a tobacco weighing apparatus 74, and a machine control unit 76. In operation, the tobacco product making machine 70 produces tobacco products, such as heated tobacco products, which are output as a mass flow. The sampling unit 72 samples tobacco products from the mass flow and feeds the sampled products to the tobacco weighing apparatus 74. The tobacco weighing apparatus 74 determines the weight of the tobacco component in the product. The tobacco weighing apparatus 74 may be an apparatus for determining the weight of tobacco in any of the forms described above. The weight of the tobacco component is fed from the apparatus 74 to the machine control unit 76. The machine control unit 76 controls the amount of tobacco which is used in the tobacco products based on the weight of the tobacco component as determined by the apparatus 74. Alternatively, the adjustments could be made manually by the machine operator based on a visual display of the tobacco weight.

It will be appreciated that embodiments of the present invention have been described above by way of example only, and modifications in detail are possible.

For example, the present invention may be used with any type of tobacco product containing a tobacco component and at least one non-tobacco component. The x-ray system may be any type of x-ray system which is able to take x-ray images of the tobacco product and output image data. Furthermore, the order in which the various steps described above are performed may be changed. Other variations in detail will be apparent to the skilled person within the scope of the claims. 

1. An apparatus arranged to determine a weight of tobacco in a tobacco product, the tobacco product comprising a tobacco component and a plurality of non-tobacco components, the apparatus comprising: a weighing device arranged to determine a total weight of the tobacco product; an imaging device arranged to produce an x-ray image of the tobacco product; and a processor arranged to: determine weights of the non-tobacco components from the x-ray image_(i), and determine a weight of the tobacco component based on the total weight of the tobacco product and the weights of the non-tobacco components.
 2. The apparatus according to claim 1, wherein the tobacco product is a heated tobacco product.
 3. The apparatus according to claim 1, wherein the tobacco component comprises reconstituted sheet tobacco.
 4. The apparatus according to claim 1, wherein the tobacco product comprises a component which produces a microwave response independent of product density when irradiated with microwaves.
 5. The apparatus according to claim 1, wherein the tobacco component is at least partially over-wrapped with a metal or metalized foil.
 6. The apparatus according to claim 1, wherein the processor is arranged to subtract the weight of each of the non-tobacco components from the total weight of the tobacco product.
 7. The apparatus according to claim 1, wherein the processor is arranged to determine a dimension of each of the non-tobacco components, and to calculate the weight of each of the non-tobacco components based on the dimension.
 8. The apparatus according to claim 7, wherein the processor is arranged to analyse the x-ray image to determine the dimension of each of the non-tobacco components, wherein the dimension is at least one of a length or a diameter of the non-tobacco component.
 9. (canceled)
 10. The apparatus according to claim 7, wherein the processor is arranged to calculate a volume or an area of each of the non-tobacco components based on the dimension.
 11. (canceled)
 12. The apparatus according to claim 7, wherein a diameter of a non-tobacco component is a predetermined value and a length of the non-tobacco component is determined from the x-ray image.
 13. The apparatus according to claim 1, wherein the processor is arranged to determine the weight of a non-tobacco component based on a volume or area of the non-tobacco component and a predetermined value of density or area density for the non-tobacco component.
 14. The apparatus according to claim 1, further comprising a storage device which stores predetermined values of density or area density of non-tobacco components for each of a plurality of different types of tobacco product, wherein the processor is arranged to look up the predetermined values of density or area density in the storage device for a product of a type which is under test.
 15. (canceled)
 16. The apparatus according to claim 1, wherein the processor is arranged to determine a type of product which is under test based on characteristics of the tobacco product in the x-ray image.
 17. The apparatus according to claim 1, wherein the imaging device comprises: a source of x-ray radiation arranged to irradiate the tobacco product; and a sensor arranged to detect x-ray radiation from the tobacco product and to produce the x-ray image.
 18. (canceled)
 19. The apparatus according to claim 17, wherein the imaging device is arranged to produce a composite x-ray image from image data produced by the sensor at a plurality of different axial positions of the tobacco product.
 20. (canceled)
 21. The apparatus according to claim 1, wherein the apparatus is an analysing apparatus for offline analysis of tobacco products.
 22. The apparatus according to claim 1, wherein the apparatus is part of a tobacco product making or combining machine.
 23. The apparatus according to claim 22, wherein the weighing device is part of the making or combining machine.
 24. The apparatus according to claim 22, wherein the weight of the tobacco component is used to control filling of the tobacco component of tobacco products produced by the tobacco product making or combining machine.
 25. A method of determining a weight of tobacco in a tobacco product, the tobacco product comprising a tobacco component and a plurality of non-tobacco components, the method comprising: determining a total weight of the tobacco product; producing an x-ray image of the tobacco product; determining weights of the non-tobacco components from the x-ray image; and determining a weight of the tobacco component based on the total weight of the tobacco product and the weights of the non-tobacco components. 